Most accidents occur on installations that are still powered on, or not completely recorded. An analysis of the causes of these accidents generally shows that a preliminary study would have allowed the area concerned to be completely de-energized. It should be noted on this point that 80% of deaths due to electricity are caused by domestic causes. That is why operations should be carried out, whenever possible, without the power. Work may be carried out under voltage when: operating conditions make it dangerous or impossible to switch off the power, or if the nature of the work requires the presence of tension. In this case, workers must have received specific training and must have special authorization. They must also have received a service instruction that indicates the requirements to be met.